Optical imaging probe

ABSTRACT

Provided is an optical imaging probe that is able to obtain a stable observation image by a dynamic pressure bearing. An optical imaging probe for guiding rearward a light entering a front end includes: a rotation driving source adapted to drive and rotate a rotor; a tubular rotation shaft inserted and fixed over an axial direction in a rotation center side of the rotor; an optical fiber inserted in the tubular rotation shaft, the front end of which a light is able to enter; and a bearing member supporting the tubular rotation shaft in a rotatable manner, and the bearing member configures a dynamic pressure bearing adapted to generate a high lubricating oil film pressure locally at multiple positions in a circumference direction.

TECHNICAL FIELD

The present invention relates to an optical imaging probe for taking and observing a light reflected by the object.

BACKGROUND ART

The image diagnosis techniques (optical imaging techniques) have been widely utilized in various sites such as device machine, semiconductor, medical treatment, and so on. For example, the X ray CT, the nuclear magnetic resonance, the ultrasonic observation, and the like are exemplified that are able to take the tomographic image in addition to the general microscopy in the manufacturing site for precision machine, semiconductor, and the like and the medical site.

In recent years, the OCT (Optical Coherent Tomography) technique that utilizes optical coherence has been paid attention as an approach of the image diagnosis. The near infrared ray with the wavelength of 1300 nm is often used for the light source, and the near infrared ray is noninvasive to the organism and is superior in the spatial resolution because of its shorter wavelength than the ultrasonic wave, which allows for the identification of approximately 10 to 20 μm and therefore, in particular, the further use in the medical site is expected. The exemplary structure of the OCT endoscope is as disclosed in Patent document 1, for example.

By the way, in the OCT endoscope disclosed in Patent document 1, the rotational force of a motor is transferred to a rotation shaft via a belt and further transferred to a lens unit via a flexible shaft extending through in an optical sheath. Therefore, ablation powder is likely to occur due to the friction between the inner circumference surface of the optical sheath and the flexible shaft, and rotation unevenness, rotation transfer delay, torque loss, and the like are likely to occur due to the friction, deflection, and/or torsion of the flexible shaft, elastic deformation of the belt, and so on.

Further, as a technique for overcoming the above-described problems, in the invention of Patent document 2, a motor is arranged so as to face the front end of an optical fiber and a reflection mirror is provided at the front end surface of the rotation shaft of the motor. In this invention, however, the body of the motor is located more front than the reflection mirror, which may cause the problems that the power supply cable for the motor may be bent toward the optical fiber side, that the power supply cable may be located in the side of the reflection mirror and block the light reflected by the reflection mirror and thus a part of the whole 360-degree circumference may be a shade resulting in the limitation of the angle of view, and that a protruding part that is more front than the reflection mirror (a part incorporating the motor body) may come into contact with the object resulting in the limitation of the imaging range in the probe axis direction. Further, when the motor is rotated continuously at a high speed, the deviation of the film pressure of the lubricating oil at the bearing part is likely to cause rotation unevenness, axis vibration, and the like called as jitter (the phenomenon in which the rotation angle fluctuates), face tangle error (the phenomenon in which the rotation end surface tilts), and whirl (the phenomenon in which the rotation axis vibrates).

RELATED ART DOCUMENT Patent Literatures

[Patent Document 1] Japanese Patent No. 3885114

[Patent Document 2] Japanese Patent No. 4461216

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention has been achieved taking into consideration of the above-described conventional circumstances, and its objects are to provide an optical imaging probe that is able to obtain a stable observation image by reducing the occurrence of the rotation transfer delay and the torque loss, preventing the rotation unevenness, the axis vibration, the friction, and the rotation transfer delay of the rotation part, and the limitation of the angle of view that a part of the whole 360-degree circumference is shaded, and preventing the limitation of the imaging range in the probe circumference direction and the axial direction.

Solutions to the Problems

One of the solutions to overcome the above problems is an optical imaging probe for guiding rearward a light entering the front end, which includes: a rotation driving source adapted to drive and rotate a rotor; a tubular rotation shaft inserted and fixed over the axial direction in the rotation center side of the rotor; an optical fiber inserted in the tubular rotation shaft, the front end of which a light is able to enter; and a bearing member supporting the tubular rotation shaft in a rotatable manner, and the bearing member configures a dynamic pressure bearing adapted to generate a high lubricating oil film pressure locally at multiple positions in the circumference direction.

Advantage of the Invention

The present invention is configured as described above, so that a stable observation image can be obtained compared to the conventional art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating an example of an optical imaging probe according to the present invention.

FIG. 2 is a cross-sectional view illustrating another example of an optical imaging probe according to the present invention.

FIG. 3 is a cross-sectional view illustrating another example of an optical imaging probe according to the present invention.

FIG. 4 is an enlarged cross-sectional view illustrating an example of a bearing member.

FIG. 5 is an enlarged cross-sectional view illustrating an example of a connection between two single-mode optical fibers.

FIG. 6 is an enlarged cross-sectional view illustrating another example of a connection between two single-mode optical fibers.

FIG. 7 is an enlarged cross-sectional view illustrating another example of a connection between two single-mode optical fibers.

FIG. 8 is a schematic view illustrating a distribution of the lubricating oil film pressure in the bearing structure of the present embodiment.

FIG. 9 is a schematic view illustrating a distribution of lubricating oil film pressure in the case of the complete-circle bearing member.

DESCRIPTION OF EMBODIMENTS

The first feature in the present embodiment includes, in an optical imaging probe for guiding rearward a light entering a front end: a rotation driving source adapted to drive and rotate a rotor; a tubular rotation shaft inserted and fixed over the axial direction in the rotation center side of the rotor; an optical fiber inserted in the tubular rotation shaft, the front end of which a light is able to enter; and a bearing member supporting the tubular rotation shaft in a rotatable manner, and the bearing member configures a dynamic pressure bearing adapted to generate a high lubricating oil film pressure locally at multiple positions in the circumference direction (see FIGS. 1 to 4).

This configuration requires no flexible shaft or belt to be interposed as seen in the conventional art (Patent document 1), allowing for the reduction of the rotation transfer delay, the torque loss, and the like. Furthermore, the dynamic pressure bearing that generates a high film pressure of the lubricating oil locally at the multiple positions in the circumference direction is configured with the bearing member, so that the lubricating oil film pressure at the bearing part can be distributed in the circumference direction and thus the rotation unevenness, the axis vibration, and the like can be reduced, which allows for obtaining a stable observation image.

Further, it is unnecessary to provide the rotation driving source more front than the optical fiber as seen in the conventional art (Patent document 2), allowing for a simple arrangement of the power supply cable, which can prevent the limitation of the imaging range in the probe circumference direction and the axial direction.

The second feature is that, in addition to the first feature, an optical path conversion element adapted to convert the direction of a light guided by the optical fiber into the intersecting direction with respect to the axial direction of the tubular rotation shaft is disposed distant from the front end of the optical fiber, and the optical path conversion element is fixed to the tubular rotation shaft (see FIGS. 1 to 3).

This configuration allows for the effective reduction of the rotation unevenness, the axis vibration, and the like of the optical path conversion element, so that the stable observation image can be obtained in the range of the angle of 360 degrees around the probe outer circumference.

The third feature is that, in addition to the first or second feature, the rotor and the tubular rotation shaft are continuously rotated at a number of revolutions of 400 rpm or more and 3600 rpm or less.

According to this configuration, the use of the dynamic bearing allows for the effective reduction of the rotation unevenness, the axis vibration, and the like that may occur when the rotor and the tubular rotation shaft are rotated continuously at a high speed.

The fourth feature is that, in addition to any one of the first to third features, the optical fiber is provided in a non-rotatable manner relatively to the tubular rotation shaft (see FIG. 1).

According to this configuration, the optical fiber is not rotated, which results in the simple arrangement of the connection part of the optical fibers and allows for the arrangement with one optical fiber. Therefore, this allows for the reduction of the optical transmission loss at the connection part of the optical fibers.

Furthermore, other feature is that the tubular rotation shaft is fixed in the rotation center side of the rotor so as to protrude out of the rotor to both sides of the axial direction, and the tubular rotation shaft is supported at its both ends by the bearing members in a rotatable manner (see FIGS. 1 to 3).

According to this configuration, the tubular rotation shaft is supported at both sides in the axial direction, which allows for the further effective reduction of the rotation unevenness, the axis vibration, and the like of the rotation part.

Furthermore, other feature is that light converging means adapted to converge the light emitted forward from the optical fiber is provided between the optical path conversion element and the front end of the optical fiber (see FIGS. 1 to 3).

This configuration allows for converging the light emitted forward from the optical fiber at the front end to effectively irradiate the object.

Next, the preferred examples of the present embodiment having the above features will be described in detail based on the drawings.

EXAMPLE 1

FIG. 1 illustrates an example 1 of the optical imaging probe according to the present invention.

The optical imaging probe includes a rotation driving source 10 adapted to drive and rotate a rotor 11, a tubular rotation shaft 20 inserted and fixed in the rotation center side of the rotor 11 in the axial direction, an optical fiber 30 inserted in the tubular rotation shaft 20 with play, the front end of which a light is able to enter, bearing members 41 and 42 supporting the tubular rotation shaft 20 in a rotatable manner, light converging means 50 adapted to converge the light emitted forward from the optical fiber 30, and an optical path conversion element 60 adapted to convert, at a position distant from the light converging means 50, the light direction into the intersecting direction with respect to the axial direction of the tubular rotation shaft 20.

This optical imaging probe is connected to the front end of a flexible long cylindrical sheath 70. Further, the starting end side (the right side in FIG. 1) of the sheath 70 is connected to an OCT (Optical Coherence Tomography) apparatus having a light source.

The rotation driving source 10 is an electric motor of the inner rotor type (see FIG. 1) including the rotatable rotor 11, an electromagnetic coil 12 covering the peripheral of the rotor 11, a cylindrical front housing 13 (stator) covering the peripheral of the electromagnetic coil 12, a substrate 14 adapted to supply electric power to the electromagnetic coil 12, and so on, and is controlled so as to continuously rotate at a predetermined number of revolutions.

The rotor 11 is arranged in a cylindrical shape having a permanent magnet, and continuously rotated by the electromagnetic effect in relation with the electromagnetic coil 12.

The electromagnetic coil 12 is provided in substantially a cylindrical manner with a predetermined clearance to the outer circumference surface of the rotor 11, and fixed to the inner circumference surface of the front housing 13 (stator) in an non-rotatable manner.

The substrate 14 is fixed to the rear end surface of the electromagnetic coil 12 in substantially an angular manner, and supplies, to the electromagnetic coil 12, the control current supplied from the power supply cable 14 a.

The power supply cable 14 a is guided rearward through a notched through part 14 b formed in a bearing member 41 and a connection member 81 described later, and is further connected to the control circuit in the OCT apparatus through inside the long cylindrical sheath 70. It is noted that the through part 14 b may be a through hole.

The front housing 13 (stator) is formed in a cylindrical shape from a magnetic material (for example, permalloy and the like), and works to enhance the electromagnetic force generated by the electromagnetic coil 12.

The bearing members 41 and 42 are supported by the front end side and the rear end side of the front housing 13. Further, a cylindrical rear housing 82 with substantially the same diameter as the front housing 13 is connected to the rear end side of the front housing 13 and the bearing member 41 via the connection member 81 that fixes and supports the optical fiber 30 from the outer circumference, and the sheath 70 is connected to the rearmost end of the rear housing 82.

The connection member 81 is substantially a column member in which the optical fiber 30 is inserted in its shaft center side and the power supply cable 14 a is inserted through the notch in its outer circumference side, and is fixed in non-rotatable manner by interposing an edge 81 a protruding outward in the radial direction from the outer circumference surface between the cylindrical front housing 13 (stator) and the rear housing 82 and fitting itself into the inner circumference surface of the rear housing 82.

The rear housing 82 is substantially a cylindrical member fitted into the outer circumference surface of the connection member 81 and, in its rear end side, communicates into the long cylindrical sheath 70.

Further, the tubular rotation shaft 20 is a long cylindrical member made of a hard material such as metal and is inserted and fixed on the rotation center side of the rotor 11, and its front end and rear end sections protrude out of the end surfaces of the axial direction of the rotor 11.

The rear end side of tubular rotation shaft 20 is supported by the bearing member 41 in its rear side in a rotatable manner, and the front end side of the tubular rotation shaft 20 is supported by the bearing member 42 in its front side in a rotatable manner and protrudes forward than the bearing member 42.

The bearing members 41 and 42 configure the dynamic bearings adapted to generate a high film pressure of the lubricating oil locally at multiple positions in the circumference direction.

Each of the bearing members 41 and 42 is formed in substantially a cylindrical shape by a hard material with a good abrasion resistance property such as bronze, sintered metal, and the like and, in its inner circumference side, the tubular rotation shaft 20 is inserted and supported in a rotatable manner interposing the lubricating oil.

In the inner circumference surface of each of the bearing members 41 and 42, as illustrated in FIG. 4, a plurality of grooves 41 a extending in the axial direction are formed by a predetermined pitch in the circumference direction. Each groove 41 a continues from one end to the other end of the bearing members 41 and 42 in the axial direction.

A plurality of grooves 41 a work so as to distribute, in the circumference direction, the pressure of the lubricating oil film (referred to as lubricating oil film pressure) inserted between each of the bearing members 41 and 42 and the tubular rotation shaft 20.

That is, if a complete-circle bearing member without the groove 41 a were used, the lubricating oil film pressure p would be offset and locally increased at a part of the inner circumference surface of the bearing member in the circumference direction as illustrated in FIG. 9, which is likely to cause rotation unevenness, axis vibration, and the like called as jitter (the phenomenon in which the rotation angle fluctuates), face tangle error (the phenomenon in which the rotation end surface tilts), and whirl (the phenomenon in which the rotation axis vibrates).

According to the bearing members 41 and 42 of the present embodiment, however, the lubricating oil film pressure p is distributed in the multiple positions corresponding to the grooves 41 a in the circumference direction and is higher near each groove 41 a as illustrated in FIG. 8. This allows for the significant reduction of the jitter, the face tangle error, the whirl, and the like.

It is noted that, while FIG. 8 schematically illustrates the bearing structure according to the present invention and the grooves 41 a, 41 a neighboring in the circumference direction are different in depth, the depth of a plurality of grooves 41 a is set to be the same in a preferred example of the present embodiment. The depth, the width, and the number of these grooves 41 a are properly set so as to effectively reduce the occurrence of the jitter, the face tangle error, the whirl, and the like. While the bearing member 41 as depicted as an example has four grooves 41 a by the same pitch, other preferred example has eight by the same pitch.

According to an example of the present embodiment, the inner diameter of the bearing or the outer diameter is approximately 0.3 mm to 1.0 mm, the gap in the radial direction is designed to the range from 1 micrometer to 3 micrometers.

Further, according to an example of the present embodiment, while the groove 41 a is provided in parallel with respect to the shaft (that is, at an angle of 90 degrees with respect to the direction in which the lubricating fluid rotates and flows) in order to provide the same performance in any case where the rotation direction of the shaft is forward or reverse, any proper angle may be provided with respect to the shaft when the rotation direction is defined in one direction, and the both allow for the preferable performance.

Further, according to the experimental result by the inventors of the present application, it has been confirmed that the design that the number of the grooves 41 a ranges four to sixteen and its depth ranges 1 micrometer to a few micrometers allows for the preferable performance, but, when out of these ranges, it is likely to degenerate the optical performance due to the rotation vibration or the vibrating rotation.

The rear bearing member 41 is fitted into the inner circumference surface of the front housing 13, has the tubular rotation shaft 20 inserted in the shaft center side and supports it in a rotatable manner, and fits the connection member 81 into the rear outer circumference surface.

Further, the front bearing member 42 is fitted into the inner circumference surface of the front end side of the front housing 13 and has the tubular rotation shaft 20 inserted in the shaft center side and supports it in a rotatable manner.

In front and rear of the front bearing member 42, provided are positioning members 21 and 22 that restrict the position in the axial direction of the tubular rotation shaft 20.

One positioning member 21 is a member fixed to the outer circumference surface of the tubular rotation shaft 20 in an angular manner at more rear than the bearing member 42 and, when the tubular rotation shaft 20 moves forward, restricts the movement by the contact with the bearing member 42.

The other positioning member 22 is a member fixed to the outer circumference surface of the tubular rotation shaft 20 in an angular manner at more front than the bearing member 42 and, when the tubular rotation shaft 20 moves rearward, restricts the movement by the contact with the bearing member 42.

Further, the optical fiber 30 includes a long axial-shaped single-mode optical fiber 31 and a protection coating 32 covering and protecting the outer peripheral of the single-mode optical fiber 31.

The single-mode optical fiber 31 is one optical fiber of single-mode type including a core in the center and a clad covering its outer peripheral. The light converging means 50 is connected to the front end side of the single-mode optical fiber 31.

The light converging means 50 is a lens that converges the light transmitted forward from the optical fiber 30 and emits it further forward. The light emitted from the light converging means 50 travels forward while being converged, is direction-converted by the optical path conversion element 60 at a position distant from the light converging means 50, and concentrates at a focal point distant from the optical path conversion element 60 (see the two-dot chain line of FIG. 1).

It is noted that, while the light converging means 50 is substantially a sphere lens according to the depicted example, it may be substantially a column-shaped GRIN lens (refractive index distribution lens), a lens with other shape, and the like as other examples.

The optical path conversion element 60 is configured to total-reflect the light emitted forward from the light converging means 50 to direct it to the intersecting direction (the direction slightly inclined forward from the orthogonal direction according to the example of FIG. 1) and, for example, may be in a form where the tip side of the column-shaped shaft member is obliquely cut and a mirror treatment is applied thereon, a form where a prism is used, and the like.

The optical path conversion element 60 is fixed to the front end (in detail, the outer peripheral of the positioning member 22) of the tubular rotation shaft 20 via a support bracket 61.

The support bracket 61 covers the light converging means 50 from the circumference direction and is formed in substantially a cylindrical shape, to the front end side of which the optical path conversion element 60 is fixed. A part of the support bracket 61 in the circumference direction is formed with a notched part 61 a for passing the light emitted from the optical path conversion element 60 outward in the radial direction.

The forefront end of the support bracket 61 is provided with a convex tip member 62. The convex tip member 62 is formed in substantially a hemisphere shape according to the depicted example and reduces the impact, damage, and the like to the object when the optical imaging probe moves forward and comes into contact with the object.

Next, the distinctive effects and advantages will be described with respect to the above-described optical imaging probe of FIG. 1.

First, in response that electric power is supplied to the rotation driving source 10 by the power supply cable 14 a, the rotation driving source 10 rotates the rotor 11, the tubular rotation shaft 20, the bracket 61 and the optical path conversion element 60, and so on continuously at a high speed. The revolving speed at this time is adjustable within the range of 0 to 3600 rpm, preferably set to 400 rpm or more and 3600 rpm or less so that the tubular rotation shaft 20 float in the lubricating oil at the bearing part, and set to approximately 1800 rpm according to the particularly preferable embodiment.

Then, in response that the starting end of the optical fiber 30 is supplied with a light (in detail, the near infrared ray) from the OCT apparatus, the light passes inside the optical fiber 30, is emitted forward in the axial direction from the light converging means 50 at the front end of the optical fiber 30, and is guided in the intersecting direction by the optical path conversion element 60 to irradiate the object. The light reflected by the object then passes the path opposite to the described above, firstly enters the light converging means 50 after reflected by the optical path conversion element 60, travels from the light converging means 50 to the optical fiber 30, and is further transmitted rearward by the optical fiber 30 back to the OCT apparatus. The OCT apparatus analyzes the returned reflected light to be imaged. Therefore, the image of the 360-degree range around the front end side of the optical imaging probe can be obtained in real time.

As described above, when rotating the optical path conversion element 60 and so on, the rotational force of the rotor 11 is transferred to the optical path conversion element 60 and the like via the tubular rotation shaft 20 that is a rigid body, so that occurrence of the rotation transfer delay, the torque loss, and the like can be reduced. Moreover, the bearing members 41 and 42 configure the dynamic pressure bearings that generate a high lubricating oil film pressure locally at the multiple positions in the circumference direction, so that the lubricating oil film pressure at the bearing part is distributed in the circumference direction to reduce the rotation unevenness, the axis vibration, and the like of the rotation part, which allows for obtaining the stable observation image as a result.

Further, employed is the structure having no main component such as the rotation driving source and the like arranged more front than the optical path conversion element 60, which allows for the simple wiring arrangement of the power supply cable 14 a and thus can prevent the imaging range in the circumference direction of the probe from being limited and the forward movement from being limited by the power supply cable 14 a.

EXAMPLE 2

Next, described will be an example 2 of the optical imaging probe according to the present invention (see FIG. 2). It is noted that, in the following description, substantially the same components as above-described example 1 will be labeled with the same reference signs, and the duplicated detailed description will be omitted.

The optical imaging probe illustrated in FIG. 2 includes a rotation driving source 10 drives and rotates a rotor 11, a tubular rotation shaft 23 inserted and fixed in the axial direction on the rotation center side of the rotor 11, a first single-mode optical fiber 33 inserted in the tubular rotation shaft 23, the front end of which a light is able to enter, a second single-mode optical fiber 34 supported in a non-rotatable manner at the rear end side of the first single-mode optical fiber 33, a gap s and optical path correcting means 35 (see FIG. 5) interposed between the first single-mode optical fiber 33 and the second single-mode optical fiber 34, bearing members 41 and 42 supporting the tubular rotation shaft 23 in a rotatable manner, light converging means 51 adapted to converge the light emitted forward from the first single-mode optical fiber 33, and an optical path conversion element 63 adapted to convert the direction of the light guided by the first single-mode optical fiber 33 into the intersecting direction with respect to the axial direction of the tubular rotation shaft 23 at the front side of the light converging means 51.

The tubular rotation shaft 23 is a long cylindrical member made of a hard material such as metal and is inserted and fixed on the rotation center side of the rotor 11, and its front end and rear end sections protrude out of the end surfaces of the axial direction of the rotor 11.

The rear end side of the tubular rotation shaft 23 is supported in a rotatable manner by the bearing member 41 at its rear side, and the front end side of the tubular rotation shaft 23 is supported in a rotatable manner by the bearing member 42 at its front side and protrudes more forward than the bearing member 42.

Further, inside the tubular rotation shaft 23, the first single-mode optical fiber 33 is inserted and fixed in its front side, and first optical correcting means 35 a is inserted and fixed in its rear side.

The first single-mode optical fiber 33 is formed with a core in the center side and a clad covering its outer peripheral. The first single-mode optical fiber 33 is formed slightly shorter than the tubular rotation shaft 23 and inserted near the front side within the tubular rotation shaft 23 with its end forming substantially a flat plane with the front end of the tubular rotation shaft 23. The first single-mode fiber 33 contacts, by its outer surface, with the inner surface of the tubular rotation shaft 23 over substantially the whole length in the axial direction and substantially the whole circumference, and rotates with the tubular rotation shaft 23 in an integral manner.

The second single-mode optical fiber 34 is disposed in the rear side of the first single-mode optical fiber 33 in a coaxial manner interposing the optical path correcting means 35 and the gap s, and supported in a non-rotatable manner.

Similarly to the first single-mode optical fiber 33, the second single-mode optical fiber 34 is formed with a core in the center side and a clad covering its outer peripheral, and its rear side other than a part of the front end side is covered with a protection coating 34 a. The rear side of the second single-mode optical fiber 34 is inserted in the sheath 70 and connected to the OCT apparatus.

The optical path correcting means 35 is configured to expand and collimate the light transmitted from one single-mode optical fiber 33 (or 34) to pass it in the gap s and then converge and guide it to the other single-mode optical fiber 34 (or 33).

With respect to the example illustrated in FIG. 5, in details, the optical path correcting means 35 includes first optical path correcting means 35 a connected to the first single-mode optical fiber 33 and second optical path correcting means 35 b connected to the second single-mode optical fiber 34 and has the gap s between these two optical path correcting means 35 a and 35 b.

The first optical path correcting means 35 a is a graded index optical fiber adapted to expand and collimate the light guided rearward from the first single-mode optical fiber 33.

The first optical path correcting means 35 a is inserted in the rear end side of the tubular rotation shaft 23 such that its rear end forms substantially a flat plane with the rear end of the tubular rotation shaft 23, and is connected to the rear end of the first single-mode optical fiber 33 in a coaxial manner inside the tubular rotation shaft 23.

While the first optical path correcting means 35 a may be connected to the first single-mode optical fiber 33 by a welding, the first optical path correcting means 35 a and the first single-mode optical fiber 33 may be arranged by a pressure welding in the axial direction as another example.

Also, the second optical path correcting means 35 b is a graded index optical fiber adapted to expand and collimate the light irradiated forward from the second single-mode optical fiber 34.

While the second optical path correcting means 35 b may be connected to the second single-mode optical fiber 34 by a welding, the second optical path correcting means 35 b and the second single-mode optical fiber 34 may be arranged by a pressure welding in the axial direction as another example.

The graded index optical fibers used as the first and second optical path correcting means 35 a and 35 b are formed in a proper length so as to expand the light irradiated from the first or second single-mode optical fiber 33 or 34 to make substantially the parallel and relatively wide light and, for example, formed in a length corresponding to one-fourth of the meandering range of the light traveling within the core or an odd multiple thereof.

It is noted that another example of the first and second optical path correcting means 35 a and 35 b may be the GRIN lens (refractive index distribution lens), other lens, and the like.

The second optical path correcting means 35 b is fixed to the inner circumference surface of the rear housing 82 in a non-rotatable manner via a cylindrical holding member 83 and a holder 84 (see FIG. 2).

The cylindrical holding member 83 is a cylindrical member covering the second optical path correcting means 35 b over the whole length and inserting the front end of the second single-mode optical fiber 34 therein.

The inner circumference surface of the cylindrical holding member 83 contacts with the outer circumference surface of the second optical path correcting means 35 b and holds the second optical path correcting means 35 b in a non-rotatable manner (see FIG. 2).

The holder 84 is a cylindrical member having a notch in a part of the outer circumference through which the power supply cable 14 a passes, and inserts and fixes the cylindrical holding member 83 at its front side of the center and inserts and fixes the protection coating 34 a of the second single-mode optical fiber 34 at its rear side (see FIG. 2).

As described above, since the gap s is secured between the first optical path correcting means 35 a and the second optical path correcting means 35 b, the first optical path correcting means 35 a is able to freely rotate.

The width of the gap s is properly set so that the light transmission can be effectively made between the first optical path correcting means 35 a and the second optical path correcting means 35 b.

In addition, in FIG. 2, the reference sign 85 represents a positioning member fixed on the outer circumference surface of the rear side of the tubular rotation shaft 23. The positioning member 85 is located between the rear bearing member 41 and the holder 84, restricts the forward movement of the tubular rotation shaft 23 by the contact with the bearing member 41, and restricts the rearward movement of the tubular rotation shaft 23 by the contact with the holder 84.

Further, in FIG. 2, the reference sign 86 represents a connection member for connecting the rear end of the front housing 13 and the bearing member 41 to the rear housing 82. The connection member 86 is substantially a column member in which the tubular rotation shaft 23 is inserted in its shaft center side in a non-rotatable manner and the power supply cable 14 a is inserted in the notch in its outer circumference side, and is fixed in a non-rotatable manner by having an edge 86 a protruding outward in the radial direction from the outer circumference surface held between the cylindrical front housing 13 and the housing 82 and fitting itself to the inner circumference surface of the housing 82.

Then, the light converging means 51 is fixed to the part protruding forward from the front bearing member 41 in the tubular rotation shaft 23 in a coaxial manner via a support bracket 64, and the optical path conversion element 63 is further fixed to the front end of the light converging means 51 in a coaxial manner (see FIG. 2).

The support bracket 64 is a cylindrical member connected to the front end of the tubular rotation shaft 23 in substantially a coaxial manner, and inserts and fixes the front end of the tubular rotation shaft 23 in its rear end side and inserts and fixes the rear end of the light converging means 51 described later in its front end side.

The light converging means 51 is located between the optical path conversion element 63 and the front end of the first single-mode optical fiber 33 and disposed in front of the first single-mode optical fiber 33 with a gap (see FIG. 2), and converges the light emitted forward from the first single-mode optical fiber 33.

While the light converging means 51 is substantially the column-shaped GRIN lens (the refractive index distribution lens) according to the depicted example, it may be replaced with a proper length of graded index optical fiber, a lens with other shape than the column, and the like as another example.

The optical path conversion element 63 is a prism adapted to convert the direction of the light emitted forward with being guided by the first single-mode optical fiber 33 and converged by the light converging means 51 into the intersecting direction with respect to the axial direction of the first single-mode optical fiber 33. According to the depicted example, the light emitted from the optical path conversion element 63 is guided in the direction slightly inclined forward from the orthogonal direction (see the two-dot chain line of FIG. 2).

Next, with respect to the optical imaging probe of FIG. 2 described above, its distinctive effects and advantages will be described in detail.

First, in response that electric power is supplied to the rotation driving source 10 by the power supply cable 14 a, the rotation driving source 10 rotates the rotor 11, the tubular rotation shaft 23, the first single-mode optical fiber 33, the first optical path correcting means 35 a, the support bracket 64, the light converging means 51, the optical path conversion element 63, and so on continuously at a high speed. The revolving speed at this time is adjustable within the range of 0 to 3600 rpm, it is preferably set to 400 rpm or more and 3600 rpm or less, and it is set to approximately 1800 rpm according to the particularly preferable embodiment.

Then, in response that a light (in detail, the near infrared ray) is supplied to the starting end of the second single-mode optical fiber 34 from the OCT apparatus, the light passes in the second single-mode optical fiber 34 and is transmitted from the front end of the second single-mode optical fiber 34 to the second optical path correcting means 35 b, transmitted from the second optical path correcting means 35 b to the first optical path correcting means 35 a via the gap s, and then transmitted from the first optical path correcting means 35 a to the first single-mode optical fiber 33.

In details of this light transmission, the light transmitted from the second single-mode optical fiber 34 to the second optical path correcting means 35 b is expanded and collimated within the second optical path correcting means 35 b, and thereby becomes relatively thick and substantially a parallel beam and passes through the gap s, and enters the rear end of the first optical path correcting means 35 a. The incident light is then converged inside the first optical path correcting means 35 a and transmitted to the first single-mode optical fiber 33.

Then, the light travels forward inside the first single-mode optical fiber 33 is emitted forward from the front end of the first single-mode optical fiber 33, enters the light converging means 51, converges inside the light converging means 51 to propagate to the optical path conversion element 63, and is direction-converted to the intersecting direction by the optical path conversion element 63 and irradiated to the object.

Further, the light reflected by the object passes the path opposite to the above, first enters the optical path conversion element 63 to be direction-converted and is transmitted rearward by the light converging means 51, the first single-mode optical fiber 33, the first optical path correcting means 35 a, the second optical path correcting means 35 b, and the second single-mode optical fiber 34 back to the OCT apparatus. The OCT apparatus analyses the returned reflection light and images the range of 360-degree peripheral of the front end side of the optical imaging probe in real time.

As described above, in rotating the optical path conversion element 63 and the like, the rotational force of the rotor 11 is transferred to the optical path conversion element 63 via the tubular rotation shaft 23 that is a rigid body without being transferred via the conventional flexible shaft, so that the occurrence of the rotation transfer delay, the torque loss, and the like can be reduced. Moreover, the bearing members 41 and 42 form the dynamic pressure bearings that generates a high lubricating film oil pressure locally at the multiple positions in the circumference direction, so that the lubricating oil film pressure can be distributed in the circumference direction allowing for the reduction in the rotation unevenness, the axis vibration, and the like of the rotation part.

Furthermore, even when a slight axis vibration occurs, since the light is expanded and collimated between the first optical path correcting means 35 a and the second optical path correcting means 35 b, the light transmission loss can be reduced.

Therefore, as a result of the above, a stable observation image can be obtained.

Further, employed is the structure that the main components such as the rotation driving source and the like are not disposed more front than the optical path conversion element 63, which allows for the simple arrangement of the power supply cable 14 a and thus can prevent the limitation of the imaging range in the probe circumference direction and the forward movement by the power supply cable 14 a.

EXAMPLE 3

Next, described will be an example 3 of the optical imaging probe according to the present invention (see FIG. 3).

In the optical imaging probe illustrated in FIG. 3, the outer diameter of the rotation driving source 10 is reduced to substantially the same as the outer diameter of the support bracket 64 compared to the optical imaging probe illustrated in FIG. 2 and thus the fundamental structure is the same as that in FIG. 2.

In FIG. 3, the reference sign 24 represents an angular spacer 24 for connecting the tubular rotation shaft 23 formed thinner than that of FIG. 2 to the support bracket 64.

Further, in FIG. 3, although the depiction of the power supply cable is omitted, the power supply cable passes in the position shifted by approximately 90 degrees in the circumference direction and passes within the notch and sheath 70 similarly to FIG. 2 and reaches the OCT apparatus from the substrate 14.

Therefore, according to the optical imaging probe illustrated in FIG. 3, similarly to that in FIG. 2, the rotational force of the rotor 11 is transferred to the optical path conversion element 63 via the tubular rotation shaft 23 that is a rigid body without transferred via the conventional flexible shaft in rotating the optical path conversion element 63 and the like, so that the occurrence of the rotation transfer delay, the torque loss, and the like can be reduced. Moreover, the bearing members 41 and 42 form the dynamic pressure bearings that generates a high lubricating film oil pressure locally at the multiple positions in the circumference direction, so that the lubricating oil film pressure can be distributed in the circumference direction allowing for the reduction in the rotation unevenness, the axis vibration, and the like of the rotation part.

Furthermore, even when a slight axis vibration occurs, since the light is expanded and collimated between the first optical path correcting means 35 a and the second optical path correcting means 35 b, the light transmission loss can be reduced.

Therefore, as a result of the above, a stable observation image can be obtained.

Further, employed is the structure that the main components such as the rotation driving source and the like are not disposed more front than the optical path conversion element 63, which allows for the simple arrangement of the power supply cable and thus can prevent the limitation of the imaging range in the probe circumference direction and the forward movement by the power supply cable.

It is noted that, while the optical imaging probes illustrated in FIG. 2 and FIG. 3 are configured with two optical path correcting means 35 a and 35 b as a preferable connecting structure of the first single-mode optical fiber 33 and the second single-mode optical fiber 34, it may be configured with a single optical path correcting means 35 c as the form illustrated in FIG. 6 and FIG. 7 as other examples.

In details, in the form illustrated in FIG. 6, the single optical path correcting means 35 c is disposed between the first single-mode optical fiber 33 and the second single-mode optical fiber 34, and the gaps s are provided between the optical path correcting means 35 c and the first single-mode optical fiber 33 and between the optical path correcting means 35 c and the second single-mode optical fiber 34, respectively.

Also in the form illustrated in FIG. 7, the single optical path correcting means 35 c is disposed between the first single-mode optical fiber 33 and the second single-mode optical fiber 34, the gap s is provided between the optical path correcting means 35 c and the first single-mode optical fiber 33, and the optical path correcting means 35 c and the second single-mode optical fiber 34 are connected in contact with each other.

In the forms illustrated in FIG. 6 and FIG. 7, the length of the optical path correcting means 35 c and the width of the gap s are properly set so that the light emitted from the optical path correcting means 35 is expanded and collimated to reduce the light transmission loss when the axis vibration may occur.

Further, while the dynamic pressure bearing (that may be referred to as the incomplete-circle dynamic pressure bearing or the multi-arc bearing) having a plurality of grooves 41 a with intervals in the circumference direction is used as the bearing members 41 and 42 in the optical imaging probes illustrated in FIG. 1 to FIG. 3, the bearing members 41 and 42 may be the dynamic pressure bearings that generate a high lubricating oil film pressure locally at the multiple positions in the circumference direction and, for example, it is possible to use a form having a plurality of grooves in the axis side with a pitch in the circumference direction, a form in which a plurality of arc members divided in the circumference direction are combined in substantially a cylindrical shape (that may be referred to as the segment bearing), and other dynamic pressure bearing. However, the complete-circle bearing is not included as these bearing members 41 and 42.

Further, while both of the front and the rear bearing members 41 and 42 are configured as the dynamic pressure bearing in the optical imaging probes illustrated in FIG. 1 to FIG. 3, either one of them may be configured as the dynamic pressure bearing and the other may be configured as other bearing including the complete-circle bearing, as another example. In this case, in the forms of FIG. 2 to FIG. 3, it is preferable that the bearing member 41 near the optical path correcting means 35 is the dynamic pressure bearing in terms of reduction of the axis displacement.

Further, while both sides of the tubular rotation shaft 20 (or 23) are supported by the bearing members 41 and 42 as a preferable form in the optical imaging probes illustrated in FIG. 1 to FIG. 3, one of the sides of the tubular rotation shaft 20 (or 23) may be supported by one bearing member 41 (or 42) only in a cantilevered beam manner as another example. In this case, in the forms of FIG. 2 to FIG. 3, it is preferable that the bearing member 41 near the optical path correcting means 35 is supported in terms of reduction of the axis displacement.

Further, while the optical imaging probes illustrated in FIG. 1 to FIG. 3 have the advantages of the reduced axis vibration and optical transmission loss when continuously rotated at a high speed, the optical imaging probe may be used in a low speed rotation or an intermittent rotation as another example.

Further, while the arrangement that the light emitted from the front end of the optical imaging probe is reflected to the object and the reflected light is taken to be transmitted to the OCT apparatus (an interactive communication arrangement) is employed in the optical imaging probes illustrated in FIG. 1 to FIG. 3, employed may be the arrangement that the reflection light from a different light source than the optical imaging probe is taken to be transmitted to the OCT apparatus (an unidirectional communication arrangement).

It is noted that there is an applicable design range in the bearing structure to which the present embodiment can be applied. That is, the smooth rotation with low rotation loss is essential, and the use of unnecessarily high viscosity lubricating fluid or the bearing design with extremely high rigidity will result in the shortage of motor output, which may degenerate the accuracy of the angular velocity of the motor and thus causes increased jitter. Contrarily, in the dynamic pressure bearing, the design with extremely low rigidity will result in the shortage of dynamic pressure even at the number of revolutions of 400 rpm, which may cause much axis vibration and thus degenerate the performance. Further, such bearing with low rigidity is likely to cause increased vibration at the number of revolutions over 3600 rpm due to the centrifugal force generated from the rotation unit (it is increased proportionally to a square of the number of revolutions) resulting in the degeneration of the performance.

The Applicants have confirmed through experiments that the revolutions speed set within 400 rpm or more and 3600 rpm or less allows for the preferable performance as optical equipment.

DESCRIPTION OF REFERENCE SIGNS

-   -   10 Rotation driving source     -   11 Rotor     -   12 Electromagnetic coil     -   13 Front housing     -   20, 23 Tubular rotation shaft     -   30 Optical fiber     -   31 Single-mode optical fiber     -   33 First single-mode optical fiber     -   34 Second single-mode optical fiber     -   35 Optical path correcting means     -   35 a First optical path correcting means     -   35 b Second optical path correcting means     -   35 c Optical path correcting means     -   41, 42 Bearing member     -   50, 51 Light converging means     -   60, 63 Optical path conversion element 

The invention claimed is:
 1. An optical imaging probe for guiding rearward a light entering a front end, comprising: a rotation driving source adapted to drive and rotate a rotor; a tubular rotation shaft inserted and fixed over an axial direction in a rotation center side of the rotor; an optical fiber inserted in the tubular rotation shaft, a front end of which a light is able to enter; and a bearing member supporting the tubular rotation shaft in a rotatable manner, wherein the bearing member includes a dynamic pressure bearing adapted to generate a high lubricating oil film pressure locally at multiple positions in a circumference direction, wherein the rotation driving source has the rotor, which is arranged in a substantially cylindrical shape, and a coil provided in a substantially cylindrical manner and configured to cover a periphery of the rotor, wherein the optical fiber is provided in a non-rotatable manner in the optical imaging probe.
 2. The optical imaging probe according to claim 1, wherein the rotor and the tubular rotation shaft are continuously rotated at a number of revolutions of 400 rpm or more and 3600 rpm or less.
 3. An optical imaging probe for guiding rearward a light entering a front end, comprising: a rotation driving source adapted to drive and rotate a rotor; a tubular rotation shaft inserted and fixed over an axial direction in a rotation center side of the rotor; an optical fiber inserted in the tubular rotation shaft, a front end of which a light is able to enter; a bearing member supporting the tubular rotation shaft in a rotatable manner, wherein the bearing member includes a dynamic pressure bearing adapted to generate a high lubricating oil film pressure locally at multiple positions in a circumference direction; and a support bracket extending from an end portion of the tubular rotation shaft, wherein an optical path conversion element adapted to convert a direction of a light guided by the optical fiber into an intersecting direction with respect to an axial direction of the tubular rotation shaft is disposed distant from the front end of the optical fiber, and the optical path conversion element is fixed to the tubular rotation shaft via the support bracket, wherein the optical fiber is provided in a non-rotatable manner in the optical imaging probe.
 4. The optical imaging probe according to claim 3, wherein the rotor and the tubular rotation shaft are continuously rotated at a number of revolutions of 400 rpm or more and 3600 rpm or less.
 5. The optical imaging probe according to claim 3, wherein the rotation driving source has the rotor, which is arranged in a substantially cylindrical shape, and a coil provided in a substantially cylindrical manner and configured to cover a periphery of the rotor.
 6. An optical imaging probe for guiding rearward a light entering a front end, comprising: a rotation driving source adapted to drive and rotate a rotor; a tubular rotation shaft inserted and fixed over an axial direction in a rotation center side of the rotor; an optical fiber inserted in the tubular rotation shaft, a front end of which a light is able to enter; and a bearing member supporting the tubular rotation shaft in a rotatable manner, wherein the bearing member includes a dynamic pressure bearing adapted to generate a high lubricating oil film pressure locally at multiple positions in a circumference direction, wherein the optical fiber is provided in a non-rotatable manner in the optical imaging probe. 